1. Field of the Invention
The present invention relates to a metal interconnection structure and a method of fabricating a metal interconnection structure, and more particularly, to a metal interconnection structure including a protective layer partially containing oxygen (O) and a method of fabricating the same.
2. Description of the Prior Art
When fabricating semiconductor integrated circuits (ICs), semiconductor devices are connected by several metallic interconnecting layers commonly referred to as multi-level interconnects. A damascene process is a convenient and predominant method for forming the multi-level interconnects. The damascene process includes etching a dielectric material layer to form a trench and/or via patterns, filling the patterns with conductive materials, such as copper, and performing a planarization process. This way, a metal interconnection structure is obtained.
Please refer to FIG. 1, which illustrates a schematic diagram of a conventional dual damascene structure. As shown in FIG. 1, a semiconductor substrate 10 includes a first low dielectric constant (low-K) material layer 12, a first copper conductive wire 14 disposed in the first low-K material layer 12, a protective layer 16 and a second low-K material layer 18 sequentially disposed on the first low-K material layer 12, and a second copper conductive wire 20 disposed in the second low-K material layer 18. The second copper conductive wire 20 is in the trench structure 24 of the dual damascene structure 22, and connects to the first copper conductive wire 14 through the via structure 26 of the dual damascene structure 22 which penetrates through the protective layer 16 between the first low-K material layer 12 and the second low-K material layer 18. Before forming the copper conductive wires, a barrier layer 28 is formed in the dual damascene structure 22, in order to prevent the copper of the copper conductive wires from diffusing into the neighboring dielectric materials. The barrier layer 28 is commonly made of titanium (Ti), titanium nitride (TiN), tantalum nitride (TaN) or tungsten nitride (WN).
The protective layer 16 can be used to prevent the copper of the first copper conductive wire 14 from diffusing into the second low-K material layer 18, and the increase of the thickness of the protective layer 16 may improve the barrier effect of the protective layer 16. However, the too thick protective layer 16 is unfavorable for the semiconductor devices with the trend of miniaturization. Accordingly, how to improve the composition of the protective layer in order to form the protective layer having a predetermined thickness and a predetermined dielectric constant is an important issue in this field.